I position my iPhone in a cradle that attaches to the windscreen, and I think that I'm not alone. This camera has a pretty unobstructed view of the road ahead, which Waze could use to produce awesomeness! I can immediately think of a number of cool things that you could do with this, depending on how much image processing you want to do. Here are some user stories for you :)

As a: User concerned about recording details for insurance purposes in the event of an accident
I would like: Waze to record the field of view in front of me on a loop of user-selectable duration and save that loop to my videos in the event of an accident (as detected by the device's accelerometer, or other means)

So that: I can review the details of any incident at a later date

As a: Waze user that likes to help other Waze users by posting traffic updates
I would like: Waze to examine the field of view in front of the vehicle (in conjunction with the GPS-detected velocity) and automatically determine if the traffic is heavy, or and prompt me to see if I want to send an update (or just do it automatically, if I've given Waze permission to do so in some settings option)

So that: I don't have to manually do this, and the frequency of updates can be greatly increased

As a: Waze user that likes to help other Waze users by posting hazard updates
I would like: Waze to examine the field of view in front of the vehicle and detect common road hazards (objects in the road, on the shoulder, etc)

So that: I don't have to manually do this, and the frequency of updates can be greatly increased

As a: Waze user that likes to help other Waze users by posting hazard updates
I would like: Waze to examine the field of view in front of the vehicle and detect if traffic or hazards that have previously been reported are now not there

So that: Other users don't get out-of-date information about events on their route

As a: Waze user that is concerned about tiredness while driving
I would like: Waze to monitor the driver's posture, eyes and motion via the front-facing camera and look for signs of tiredness
So that: I can recieve a loud alert in the event that I inadvertantly become drowsy, which either suprises me into a more alert state so that I can safely stop, or alerts other occupants of the vehicle to the situation

OK, that's some camera ideas. Here are some other ones:

As a: Driver planning a long journey
I would like: Waze to (have the option to) prompt me to stop approximately every two hours and propose some local stopping place (service station, restaurant, cafe, hotel, etc)

So that: I find it more difficult to accidentally drive for unadvisably long periods

As a: Driver that is travelling with at least one other person in the vehicle
I would like: To be able to install a "Waze: Co-pilot" app on an iPad (Air, mini, pro, etc) that would interact with the current Waze app (lets call it "Waz; Navigator") and allow the vehicle's "co-pilot" to analyse various navigation options on the "secondary" device and make course changes that will be seen on the "navigator" device.

So that: The driver doesn't have to be distracted with making changes and decisions while the vehicle is in motion

As a: Driver, with a co-pilot receiving, receiving a prompt to stop
I would like: Information to be presented to the co-pilot to be sourced from some third-party travel information provider, such as Trip Advisor

So that: We can crowd source reviews of the standard of stopping places

As a: Driver without a co-pilot receiving a prompt to stop
I would like: To simply be told to stop "at the next available stopping place"

So that: I'm not needlessly distracted from the task of driving the vehicle

As a: Waze user who wants to see additional, non-traffic, information on the map
I would like: To be able to see a variety of "overlays" on top of the current Waze map

So that: I can see things like the wind speed and direction on the road ahead, or the amount of rain, or the temperature (in case of ice, for example), or the gradient of the terrain

As a: Waze user that has placed the device out of easy reach
I would like: Waze to listen for the direction "Waze!" and be able to perform various tasks through voice interactions
So that: I can drive with minimal distraction due to trying to interact via touch
[
I'm thinking something like:
"Waze, report heavy traffic"
"Waze, report hazard on the shoulder of this carriageway"
"Waze, plot route to <some kind of address>"
"Waze, take me home"
"Waze, reroute around an obstruction for 5 miles"
]